Online services generally employ protocols intended to preserve the confidentiality of the electronic transactions carried out. In particular, online services guarantee the anonymity of users through the use of session keys. When a user connects to a service, the user is assigned a session key. That key is used to encrypt the information exchanged between the user and the service provider system.
Some online service systems include means for revealing the session key in the event of fraudulent use of the service. Revealing the session key leads to revealing the identity of the dishonest user and consequently removes the anonymity of that user.
User anonymity removal means necessarily employ detection means adapted to command the removal of anonymity if certain conditions in respect of fraudulent use are satisfied. Such means must therefore be able to determine whether there has been fraudulent use or not.